Increasing the ionization and transmission efficiency in electrospray ionization mass spectrometry using an array of emitters and a multi-inlet interface

ANYL 435

Jason S. Page, jason.page@pnl.gov, Ryan T. Kelly, Ioan Marginean, Keqi Tang, and Richard D. Smith, rds@pnl.gov. Pacific Northwest National Laboratory, P.O. Box 999 (K8-98), 3335 Q. Ave., Richland, WA 99352
The sensitivity of ESI-MS is largely determined by the efficacy with which gas-phase ions are created (ionization efficiency) and the ability to transfer the charged species to the mass analyzer (transmission efficiency). We have significantly increased the ionization efficiency for ESI by constructing an array of individual ES emitters, which divides the 1-2 mL/min flow rate from liquid chromatography separations into multiple < 100 nL/min flows generating an array of stable nano-electrosprays. This provides the benefits of nanoESI at higher flows and increases the overall spray current. To take full advantage of the increased ES currents, we have mapped the current losses in an ESI interface. The ES plume was spatially profiled and the ES current losses on the front and inside of the inlet capillary were characterized. In addition, the amount of gas-phase analyte ions in the transmitted ES current was determined. These results were used to design a multi-capillary inlet with improved transmission efficiency and increased sampling of the expanded ES plume from the multi-ESI emitter array. Combining these technologies with an electrodynamic ion funnel increased the sensitivity by more than an order of magnitude compared to a standard ESI interface.